Fusing rollers currently used in fusing toners can be of multilayered construction. A two-layer fusing roller frequently comprises a cylindrical base core covered with a silicone elastomer cushion layer and coated thereon a fluoroelastomer fusing surface layer. Fluoroelastomer fusing surface layers have a propensity to interact with toners and cause premature offsets. They are used in conjunction with functional polydimethyl siloxane (PDMS) release oils and are resistant to penetration by the silicone release oils. However, due to poor adhesion of fluoroelastomer layers to silicone elastomers, the inner silicone elastomer surface must be modified before the fluoroelastomer is applied. This modification may include treatment with a primer, addition of an adhesive layer, or surface treatment including corona discharge treatment (CDT), plasma treatment or flame treatment.
U.S. Pat. No. 5,217,837 (Henry et al.) describes fusing rollers having a surface comprising fluoroelastomers such as Viton GF applied as a relatively thin layer overcoated on a relatively thicker layer of a thermally conductive high temperature vulcanized (HTV) silicone elastomer base cushion layer. Such layers are prone to failure by delamination of the fluoroelastomer from the silicone elastomer at an unpredictable period of use or time. To improve the bonding between their HTV silicone elastomer and fluoroelastomer layers and reduce the rate of failure by delamination or debonding, Henry et al. teach the combination of an amino silane primer layer and an adhesive layer. The adhesive layer is prepared by adding vinyl containing silicone coupling agents to a fluoroelastomer solution. The primer layer and the adhesive layer are interposed between a thermally conductive silicone base cushion layer and a fluoroelastomer surface layer as shown below:
______________________________________ Fluoro- HTV silicone Silane primer Adhesive elastomer Core rubber layer layer layer surface layer ______________________________________ vinyl containing Union Carbide vinyl con- Viton GF silicone peroxide A1100. Amino taining silane cured Al.sub.2 O.sub.3, BN propyl triethoxy- coupling fillers silane agent DC3-6060 + Viton GF/15CuO ______________________________________
U.S. Pat. No. 5,534,347 (Chen et al.) describes multilayered fusing rolls provided with an underlying silicone elastomer layer coated with a strongly adhesive fluorocarbon silicone based polymeric composition without prior CDT of the elastomer surface. However, if desired, CDT can still be performed without loss of adhesive strength. In order to achieve the desired adhesive strength, the coating composition contains a hard silicone mixture with fluorocarbon elastomer creating an interpenetrating network of the individually cured polymers. Chen's structure is represented below:
______________________________________ Core Silicone elastomer layer IPN adhesive barrier Silicone surface layer layer ______________________________________
U.S. Pat. No. 5,332,641 (Finn et al.) describes a fuser member having an amino silane adhesive layer between the surface of the aluminum core base member and the fluoroelastomer fusing surface. Finn's structure is represented below:
______________________________________ Core Silane coupling agent Viton GF base coat Fluoroelastomer A1100 and Viton GF layer (Viton GF) adhesive layer surface layer ______________________________________
There is still a need, however, for coating compositions that provide strong adhesion of the fluoroelastomer outer fusing surface layer to the silicone elastomer base cushion layer. Such compositions are needed to decrease the rate of fuser member failure due to delamination of the fluoroelastomer outer surface layer from the silicone elastomer base cushion layer.